Analog-display devices, such as dial gauges and the like with moveable indicators are widely used in innumerable applications including, for example, motor vehicle instrument panel gauges. Gauges presently used in instrument panels generally have drive means which are either locally or remotely mounted. Frequently this requires mounting the drive means to the underside or back surface of the display face of the device, and passing a drive member through the display face to the indicator. Considerable complexity, component and assembly costs, and weight are often involved in use of such
Technologies for microfabrication of miniature devices often are referred to as MEMS for microelectromechanical systems. MEMS technologies include those that employ the thin-film deposition and patterning procedures of the silicon electronics industry. Cost efficiencies can be achieved through batch processing of silicon wafers. MEMS techniques have been used, for example, in bulk micromachining of pressure sensors and accelerometers. More recently, thin films of polycrystalline silicon supported on a sacrificial layer have been used to produce even smaller versions of such devices. Miniature electrostatic motors and electrically driven actuators also have been fabricated using MEMS. A new microfabrication technology known as LIGA (an acronym taken from German words referring to lithography, electroplating and injection molding) expands MEMS to designs based on plastics, metals, alloys and ceramics. LIGA also supports batch processing and uses all of the thin-film technologies of the silicon-based electronics industry. A common feature of LIGA and silicon micromachining is that both processes typically begin with a photolithography step. LIGA is further and more critically characterized as a process employing highly collimated x-rays from a synchrotron to do the lithographic projection. In LIGA a two-dimensional pattern is projected into a thick polymer film forming a latent image. This image is then developed by chemical removal of the exposed regions leaving a three-dimensional structure having patterned features with relatively high aspect ratio: wall height divided by feature width. Surface micromachining of poly-Si typically produces features with minimum widths of 1 to 2 microns (.mu.m) and equivalent heights; giving aspect ratios of unity. In the LIGA process minimum feature sizes of 2 .mu.m width by 300 .mu.m height are routine; thus obtaining aspect ratios on the order of 100.
The LIGA process has been commercialized by MicroParts, GmbH (Karlsruhe, Germany), through an association with the Karlsruhe Nuclear Research Center, and has been used to make microdevices with movable parts, for example, microturbines, movable spring elements and acceleration sensors with stationary electrodes and movable seismic mass members. Other exemplary devices produced using such technologies include: a microturbine with a 150 .mu.m diameter rotor; micro-electrostatic motor with 0.6 mm rotor diameter; an electrostatic linear actuator; optic fiber multiplexer/demultiplexer with 10 fibers; copper coils with 20 .mu.m by 100 .mu.m conductors wound with 20 .mu.m spacings; 12-tooth gears 80 .mu.m in diameter by 140 .mu.m height with 28 .mu.m center bore, pulleys, pulley-belts, assembled gear trains and clamps.
Other MEMS technologies applicable to the present invention include those referred to as MPP-MEMS ("micropatterned polymers for MEMS"). Instead of using PMMA resist and synchrotron exposures as in LIGA, the MPP-MEMS approach is to use a photosensitive polyimide as the resist and expose it with ultra violet light. Electroforming is then used to form devises and features in the patterned polyimide. The minimum feature size typically is not as small as in LIGA and the aspect ratio not as high.